The author presents some reflections about the type of pathology - subtle, malicious and today, in her opinion, very frequent - that ranges decidedly serious clinical situations to other situations that are at the limit of so-called normality. Beginning with the title, she uses the term "bad faith" borrowed from Madeleine Baranger; she explains, however, that it only approximately corresponds to the meaning that she attempts to put into focus in this disorder. The author's reflections begin with the clinical difficulties experienced with certain patients who seemed to host with themselves strongly contradictory aspects without showing any sign of conflict or unease. This particularity was noted above all in relation to moral questions, abstract ethical codes, and ideologies proclaimed by some of the patients that were in definite contrast with their behaviour and emotions.